1. Technical Field
This invention relates generally to linear motion assemblies, and more particularly to linear motion assemblies having load bearing ball recirculation mechanisms.
2. Related Art
Linear motion assemblies, such as ball screw assemblies, for example, are used to effect linear actuation in various industries, such as machine tool, automotive, aircraft and aerospace, for example. Typically, a commercial ball screw assembly includes a screw with a continuous external helical ball groove and a ball nut with a continuous internal helical ball groove. The external helical ball groove of the ball screw and the internal helical ball groove of the ball nut are configured with substantially identical uninterrupted leads. With the ball nut received coaxially about the ball screw, the respective internal and external helical ball grooves are arranged opposite one another in radially aligned relation and a plurality of balls are disposed in a single continuous helical ball raceway formed between the opposed, continuously aligned internal and external helical ball grooves.
Typically, a ball return mechanism is incorporated in the ball nut to maintain the balls within the ball nut and within the ball raceway as the ball nut and screw move axially relative to one another. The ball return mechanism typically includes a pair of tubes or inserts disposed adjacent axially opposite ends of the ball nut, wherein the tubes or inserts are configured to recirculate the balls from the raceway adjacent one end of the nut to the opposite end of the raceway adjacent the opposite end of the ball nut. Accordingly, during recirculation, the balls traverse generally parallel to a central longitudinal axis of the assembly over a plurality of turns of the ball screw and ball nut helical grooves. Though the known tube and insert ball return mechanisms are generally effective in use, difficulties can arise from time to time. One such problem is when the balls become jammed within the raceway, particularly at the location of the ball return mechanism. In addition, manufacture and assembly of the tubes or inserts can prove challenging due to the need to having precisely configured and oriented structural features, particularly at the ends of the return mechanisms. The ends must be precisely configured so that they can pick or scoop up the balls from the raceway in the desired fashion.
Accordingly, the mechanisms used for recirculation of balls within linear motion assemblies along with the cost associated with their manufacture and the overall cost associated with the manufacture and assembly of linear motion assemblies can be improved.